Therapeutic insulin is of three basic types: fast-acting, intermediate-acting and long-acting. Insulin users often use a combination of two types of insulin depending on the user's blood sugar level, the time of day, nourishment intake and expected activity. For example, insulin injected at the beginning of an active day may have more of the fast-acting insulin, while the insulin injection given at the end of the day before going to bed would likely have more intermediate or long-acting insulin.
One of the problems with conventional insulin syringes is that they are designed to inject only one type of insulin, not a combination. Although insulin can be obtained as a mixture of the two types, the mixtures are generally a preset combination, such as 70% intermediate-acting and 30% fast-acting. Thus, the prior art limits the insulin user to a set mixture of the two insulins or the need to make two separate injections.
Another problem relates to pharmaceuticals which are kept in a lyophilized (dried) condition until use; they are then mixed with a diluent to reconstitute the pharmaceutical. This is conventionally done by syringe transfer.